It is demonstrated that the protocols developed for the cryopreservation of Heterorhabditis bacteriophora could be successfully applied to strains of the H. bacteriophora species complex and to members of the North West European species of Heterorhabditis. However the currently available protocols were not suitable for cryopreserving the Irish or the tropical Heterorhabditis species. Therefore, the postcryopreservation viabilities of Heterorhabditis species in response to preincubation in a range of cryoprotectants at varying concentrations and incubation times were determined. Species and strain specific differences in cryopreservation response were observed among Heterorhabditis isolates and optimal conditions were developed for the cryopreservation of Irish, NW European and tropical isolates of Heterorhabditis. These optimum conditions are described in this paper.